Chromatography of Candy Coatings

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					                     Chromatography of Candy Coatings
Prelab Questions:

   1. Define decant, why do we do this in this lab??
   2. Define solubility, how does this property make chromatography work??
   3. How will a chromatograph differ in a mixture compared to a pure substance?


   1. Put ~ 150 ml of water in a beaker and heat it on a hotplate.
   2. Place 6 candies of your assigned colour in a large test tube, add 7 ml of water and
       then 3 drops of concentrated acetic acid.
   3. When the colour is dissolved decant off the liquid into a clean test tube leaving
       behind the candy residue behind. Add a 20 cm piece of wool yarn and 3 drops of
       acetic acid.
   4. Put the test tube with the yarn and liquid dye into the boiling water for ~ 5 min or
       until the dye had been absorbed by the yarn.
   5. Remove the test tube from the boiling water and remove the yarn from the test
       tube with tweezers. Rinse the yarn with tap water for a minute to remove the
   6. Put the yarn into a clean test tube, add 5 ml of ammonia water and boil for 5 min
       or until the colour has left the yarn. Remove the yarn, rinse and discard.
   7. Pour the coloured water from the test tube into a watch glass. Place the watch
       glass on the beaker of boiling water. Dry off the solution until there is only ~1ml
   8. Using a micropipette spot the bottom of a chromatography strip. Put in a large
       test tube in a flask. There should be a small amount of water on the bottom of the
       test tube (below the spot).
   9. Let the chromatograph run for ~ 15-20 min. Remove the chromatograph and
       mark the water line right away!!
   10. Calculate the Rf values for each spot. Rf (ratio of the fronts = distance of solute
       divided by distance of solvent), record in data table.


Initial Colour
Final Colour(s)
Distance Solvent
moved (cm)
Distance Colour(s)
moved (cm)

Class Average Rfs

   1. This separation method is based on what two properties?

   2. Which colours are pure substances??? Which are mixtures??

   3. A sample chromatography is shown below. Use a ruler to determine the Rf for
      each dye.

   4. If sample A has an Rf of 0.80 and sample B has an Rf of 0.35 with the solvent
      traveling 15.0 cm. How far did each sample travel?

   5. Why is preferable to use a pencil rather pen to put marking on the
      chromatography paper.

   6. Why is it impossible to have an Rf value larger than 1.00?

Conclusion: In a paragraph format discuss the process of chromatography. What is the
purpose of chromatography, how does it work, what is it used for?

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